1. Field of the Invention
The present invention relates to a nitride semiconductor light emitting device capable of emitting light in blue to ultraviolet regions and, more specifically, to a structure of a nitride semiconductor light emitting device using an Si substrate.
2. Description of the Background Art
Conventionally, it has been known that a nitride semiconductor light emitting device may be used as a blue light emitting device. Recently, blue light emitting diodes and violet semiconductor laser have been studied. FIG. 11 shows a schematic structure of a nitride semiconductor light emitting device disclosed in Japanese Patent Laying-Open No. 2001-7395. The nitride semiconductor light emitting device has such a structure in that on an Si substrate 100, a lower clad layer 200 of an n type nitride semiconductor, a light emitting layer 300 and an upper clad layer 400 of a p type nitride semiconductor are stacked in this order, with a p type ohmic electrode 500 formed on upper clad layer 400 and an n type ohmic electrode 600 formed on Si substrate 100.
Consider the structure of the nitride semiconductor light emitting device disclosed in Japanese Patent Laying-Open No. 2001-7395 in which a n type nitride semiconductor layer and a p type nitride semiconductor layer are stacked successively on Si substrate. When a current blocking structure or a current constricting structure is to be formed in order to improve light emitting efficiency in the light emitting device, it is necessary to form an insulating film or a current blocking film, on a p type nitride semiconductor layer, which is doped with Mg (magnesium), thin and has high resistivity.
Therefore, conventionally, the p type nitride semiconductor layer is damaged when the insulating film or the current blocking film is formed, resulting in crystal defects generated in the p type nitride semiconductor layer, which crystal defects capture Mg. Further, in most cases, the insulating film contains oxygen, and the oxygen introduced to the surface and to the inside of the p type nitride semiconductor layer oxidizes Mg. Therefore, concentration of Mg as the impurity in the p type nitride semiconductor layer decreases, further increasing the resistivity and deteriorating characteristics of the light emitting device.
Further, when the insulating film or the current blocking film is to be formed on the p type nitride semiconductor layer as described above, the step of fabrication of such a film is necessary.
Because of these problems, it has been difficult to form a current blocking structure or a current constricting structure in the light emitting device.